post.rb

class Post
  extend  ActiveModel::Naming
  include ActiveModel::Validations
  include ActiveModel::Conversion

  validates :title, :presence => true

  def self.find(id)
    new.tap { |l| l.record = self::Record.find(id) }
  end

  def initialize(attrs = {})
    self.attributes = attrs
  end

  attr_writer :record

  delegate :id, :title, :title=, :persisted?, :to_param, :destroy, :to => :record

  def save
    valid? && record.save! && true
  end

  def attributes=(attrs = {})
    attrs.each { |k, v| self.public_send "#{k}=", v } if attrs
  end

private

  def record
    @record ||= self::Record.new
  end

  class Record < ActiveRecord::Base
    set_table_name :posts
  end
end